> Reusing an existing building can significantly reduce embodied carbon » « Joy Gai, Asia Pacific Programs Head at the World Green Building Council Old buildings, champions of energy optimization Furthermore, in Europe, the age of buildings, particularly urban buildings, may well prove to be an asset rather than a disadvantage. Admittedly, in most cases it will be necessary to make thermal adjustments: changes to joinery or to internal or external insulation, where possible. But according to the General Directorate of Urban Planning, Housing and Construction in France, old buildings, provided they are well maintained, can boast better hygrothermal behavior than some more recent buildings. That is to say, better regulation of the temperature and humidity of the air. This is particularly the case when their orientation has been optimized in relation to the sun, wind and rain, and they are built of cut stone, wood or clay. They then allow the water vapor to pass through better. Made from mostly recyclable materials, these old European buildings could be an interesting model of sustainable construction. In addition, during renovation, old buildings are often densified, improved or even raised. This makes it possible to house more people in the same place and to contain urban sprawl, also containing the artificialization of the soil in the process. This logic has been in place in many European countries since 2011 when the Net Zero Artificialization protocol was signed. What is the aimof this? To limit any increase in the area of occupied land by 2050 and to compensate for any new artificialization of land by equivalent renaturation. Finally, the buildings of these old cities sometimes hold centuries of history. From the quintessentially Parisian Haussmann buildings to the workers' housing developments of the interwar period, right through to the medieval style or the colorful wooden houses typical of Scandinavian countries. Even if their value is not always architectural, these constructions tell a story that must be passed on to future generations. Suburban areas, poor land tenure and opportunities for renovation Admittedly, the architecture found in the outskirts of major Western cities does not necessarily boast the same heritage value. Whether it is high or low-rise buildings or single-family homes, we tend to see many more standardized constructions that are often not particularly energy efficient or made of high-quality materials. The houses in housing developments, also known as ’tract housing’, were often built quickly and cheaply between 1950 and 1980, to bring the comfort of modern life to a rapidly growing population5. The most emblematic example of this standardized post-war suburban architecture is Levittown in Pennsylvania (USA). This giant housing development, considered the first of its kind, consists of 17,311 single-family homes, designed in the style of one of six different models and built according to an industrialized prototype in 26 stages. Would it be necessary to knock them all down to reconstruct new buildings, as often happens in Japan, after 20 or 30 years6? The answer is no. Faced with an endless housing crisis – goods that are too rare or too expensive – these apartment buildings, disused industrial sites, dilapidated public buildings, or even unused parking lots are excellent candidates for redevelopment. They even represent real opportunities to densify peripheral urban areas that are still too sparse. And in order to achieve this while limiting the carbon cost of the renovation, architects can now rely on the qualities of the building: its layout, volume, structure and materials that can be preserved or even reused elsewhere. They can also look to light construction methods that save considerable time, while ensuring high performance. 5. 10 Architectural Sins Committed in Suburbia — Architizer 6. Raze, rebuild, repeat: why Japan knocks down its houses after 30 years — The Guardian 33 CONSTRUCTING A SUSTAINABLE FUTURE
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